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PubMed1998

A case report of remarkable improvement of motor disturbances with L-dopa in a patient with post-diffuse axonal injury.

A 9-year-old girl with rigidospastic quadriplegia as post-traumatic sequela was reported. The distribution of lesions observed on a MRI implied diffuse axonal injury; involvement of the substantia nigra was also detected. L-Dopa administration was remarkably effective for relief of the rigidity. As a result, she became able to walk on her knees and communicate by writing letters. L-Dopa administration should be considered for patients who show rigidity as sequela of diffuse axonal injury with involvement of the substantia nigra.

Accidents, Traffic↗
PubMed2005

MRI-based finite-element analysis of left ventricular aneurysm.

Tagged MRI and finite-element (FE) analysis are valuable tools in analyzing cardiac mechanics. To determine systolic material parameters in three-dimensional stress-strain relationships, we used tagged MRI to validate FE models of left ventricular (LV) aneurysm. Five sheep underwent anteroapical myocardial infarction (25% of LV mass) and 22 wk later underwent tagged MRI. Asymmetric FE models of the LV were formed to in vivo geometry from MRI and included aneurysm material properties measured with biaxial stretching, LV pressure measurements, and myofiber helix angles measured with diffusion tensor MRI. Systolic material parameters were determined that enabled FE models to reproduce midwall, systolic myocardial strains from tagged MRI (630 +/- 187 strain comparisons/animal). When contractile stress equal to 40% of the myofiber stress was added transverse to the muscle fiber, myocardial strain agreement improved by 27% between FE model predictions and experimental measurements (RMS error decreased from 0.074 +/- 0.016 to 0.054 +/- 0.011, P < 0.05). In infarct border zone (BZ), end-systolic midwall stress was elevated in both fiber (24.2 +/- 2.7 to 29.9 +/- 2.4 kPa, P < 0.01) and cross-fiber (5.5 +/- 0.7 to 11.7 +/- 1.3 kPa, P = 0.02) directions relative to noninfarct regions. Contrary to previous hypotheses but consistent with biaxial stretching experiments, active cross-fiber stress development is an integral part of LV systole; FE analysis with only uniaxial contracting stress is insufficient. Stress calculations from these validated models show 24% increase in fiber stress and 115% increase in cross-fiber stress at the BZ relative to remote regions, which may contribute to LV remodeling.

Animals↗
PubMed2003

Diffuse white matter lesions in carbon disulfide intoxication: microangiopathy or demyelination.

Long-term exposure to carbon disulfide (CS(2)) may induce diffuse encephalopathy with parkinsonism, pyramidal signs, cerebellar ataxia, and cognitive impairments, as well as axonal polyneuropathy. The pathogenic mechanisms of diffuse encephalopathy are unclear, although vasculopathy and toxic demyelination have been proposed. Recently, we have encountered a patient who developed headache, limb tremors, gait disturbance, dysarthria, memory impairment, and emotional lability after long-term exposure to CS(2). The brain magnetic resonance images (MRI) showed diffuse hyperintensity lesions in T(2)-weighted images in the subcortical white matter, basal ganglia, and brain stem. The brain computed tomography perfusion study revealed a diffusely decreased regional cerebral blood flow and prolonged regional mean transit time in the subcortical white matter and basal ganglion. To our knowledge, there have been few reports demonstrating diffuse white matter lesions in chronic CS(2) encephalopathy using brain MRI. In addition, the (99m)Tc-TRODAT-1 single photon emission computed tomography showed a normal uptake of the dopamine transporter, indicating a normal presynaptic dopaminergic pathway. We conclude that diffuse white matter lesions may develop after chronic exposure to CS(2), possibly through microangiopathy. In addition, CS(2) poisoning can be considered as one of the causes of chronic leukoencephalopathy.

Brain↗
PubMed2005

Sodium magnetic resonance imaging of chemotherapeutic response in a rat glioma.

This study investigates the comparative changes in the sodium MRI signal and proton diffusion following treatment using a 9L rat glioma model to develop markers of earliest response to cancer therapy. Sodium MRI and proton diffusion mapping were performed on untreated (n = 5) and chemotherapy 1,3-bis(2-chloroethyl)-1-nitrosourea-treated rats (n = 5). Animals were scanned serially at 2- to 3-day intervals for up to 30 days following therapy. The time course of Na concentration in a tumor showed a dramatic increase in the treated brain tumor compared to the untreated tumor, which correlates in time with an increase in tumor water diffusion. The largest posttreatment increase in sodium signal occurred 7-9 days following treatment and correlated to the period of the greatest chemotherapy-induced cellular necrosis based on diffusion and histopathology. Both Na MRI and proton ADC mapping revealed early changes in tumor sodium content and cellularity. This study demonstrates the possibility of Na MRI to function as a biomarker for monitoring early tumor treatment and validates the use of monitoring changes in diffusion MRI values for assessing tumor cellularity.

Animals↗
PubMed2006

Detection of the ischemic penumbra using pH-weighted MRI.

The classic definition of the ischemic penumbra is a hypoperfused region in which metabolism is impaired, but still sufficient to maintain cellular polarization. Perfusion- and diffusion-weighted MRI (PWI, DWI) can identify regions of reduced perfusion and cellular depolarization, respectively, but it often remains unclear whether a PWI-DWI mismatch corresponds to benign oligemia or a true penumbra. We hypothesized that pH-weighted MRI (pHWI) can subdivide the PWI-DWI mismatch into these regions. Twenty-one rats underwent permanent middle cerebral artery occlusion and ischemic evolution over the first 3.5 h post-occlusion was studied using multiparametric MRI. End point was the stroke area defined by T(2)-hyperintensity at 24 h. In the acute phase, areas of reduced pH were always larger than or equal to DWI deficits and smaller than or equal to PWI deficits. Group analysis showed that pHWI deficits during this phase coincided with the resulting infarct area at endpoint. Final infarcts were smaller than PWI deficits (range 65% to 90%, depending on the severity of the occlusion) and much larger than acute DWI deficits. These data suggest that the outer boundary of the hypoperfused area showing a decrease in pH without DWI abnormality may correspond to the outer boundary of the ischemic penumbra, while the hypoperfused region at normal pH may correspond to benign oligemia. These first results show that pHWI can provide information complementary to PWI and DWI in the delineation of ischemic tissue.

Animals↗
PubMed2001

Reperfusion demonstrated by apparent diffusion coefficient mapping after local intra-arterial thrombolysis for ischaemic stroke.

Diffusion-weighted MRI (DWI) is becoming important for diagnosis and investigation of acute cerebral ischaemia. It has been reported that apparent diffusion coefficient (ADC) maps could be an indicator of reperfusion. Our aim was to use echo-planar technology to investigate this phenomenon. We report 19 patients treated by local intra-arterial thrombolysis for middle cerebral artery stroke within 6 h of the onset of symptoms, in whom we performed follow-up DWI. ADC were found to be higher in the patients with angiographically proven reperfusion.

Adult↗
PubMed2001

Neuronal damage in the interval form of CO poisoning determined by serial diffusion weighted magnetic resonance imaging plus 1H-magnetic resonance spectroscopy.

In a patient with the interval form of carbon monoxide (CO) poisoning diffusion weighted MRI and proton magnetic resonance spectroscopy (1H-MRS) were serially performed immediately after the appearance of delayed sequelae (the 23rd day after exposure). During the period in which few clear findings were evident on MRI T2 weighted images, a high signal area in the cerebral white matter and relative decrease in the apparent diffusion coefficient (ADCav) were already apparent on diffusion weighted images, with these findings thought to sensitively reflect the tissue injury associated with the onset of sequelae. The decrease in relative ADCav persisted until the 38th day after exposure. Subsequently, ADCav gradually increased, and in the cerebral white matter showed higher values in the 118th day after exposure than immediately after the onset of sequelae. During this period, on 1H-MRS choline containing compounds showed persistently high values throughout the course, with N-acetylaspartate depletion and the appearance of a lactate peak later in the course. These findings, with regional specificity in the cerebral white matter, reflect the developmental process of the white matter lesions in the interval form of CO poisoning in which demyelination progresses leading to neuronal necrosis. Serial diffusion weighted imaging plus 1H-MRS measurements are useful in determining the tissue damage and long term outcome of delayed sequelae associated with the interval form of CO poisoning.

Brain↗
PubMed1987

Guideline report. Projecting MRI utilization: two new approaches.

In today's competitive marketplace, hospitals must carefully analyze the financial impact of acquiring new technologies. The high cost of magnetic resonance imaging (MRI), one of the most prominent new technologies, makes it critical for hospitals to evaluate thoroughly the financial risks of providing this service. To determine whether it is likely to generate a sufficient number of MRI scans to break even financially, a hospital must carefully analyze its patient case mix. In 1984, the American Hospital Association (AHA) developed a method, the AHA MRI Utilization Model, for performing such an analysis. The original AHA model projected a hospital's potential demand for MRI procedures based on an analysis of that hospital's inpatient discharge data. The widespread use of the original AHA MRI Utilization Model by over 500 hospitals and a number of state health planning agencies has significantly influenced the diffusion of MRI throughout the United States. The original AHA model had several limitations, however: it ignored scans that might be performed to evaluate secondary diagnoses; its estimate of follow-up scans and replacement of CT by MRI was based on information from 1978; and it lacked a mechanism for considering outpatient scans. These limitations, together with the rapid evolution in clinical applications for MRI, led the AHA to improve its original MRI utilization projection methodology. In 1986, the AHA developed a new second generation MRI Utilization Model that employs two independently derived methodologies. The AHA's revised ICD-9-CM Projection method was developed by Richard diMonda, M.S.B.M.E., M.B.A.; the Diagnosis Related Groups (DRG) Projection Method was developed by Earl P. Steinberg, M.D., M.P.P. The second generation model has several advantages over the original model: it utilizes the opinions of a greater number of experts, as well as experts from more varied backgrounds; experts' opinions were obtained in 1986, rather than 1984, and so are more relevant to current patterns of practice; experts' opinions are employed to project CT, as well as MRI volume when both technologies are available, and the extent to which MRI will replace CT; total inpatient and outpatient scans are calculated; and hospital-specific adjustment factors are used to adjust for variations in patterns of practice across institutions. The DRG projection method also adds the ability to consider MRI and CT scans used to evaluate comorbid conditions and complications, as well as scans performed on patients who turned out to have no pathology. In addition, the DRG method provides a projection of potential MRI and CT volume in 1990, as well as currently.

Diagnosis-Related Groups↗
PubMed2003

Circular spectrum mapping for intravoxel fiber structures based on high angular resolution apparent diffusion coefficients.

A method is presented for mapping intravoxel fiber structures using spectral decomposition onto a circular distribution of measured apparent diffusion coefficients (ADCs). The zeroth-, second-, and fourth-order harmonic components of the ADC distribution on the circle spanned by the major and median eigenvectors of the diffusion tensor can be used to provide quantitative indices for isotropic, linear, and fiber-crossing diffusion, respectively. A diffusion-weighted MRI technique with 90 encoding orientations was implemented to estimate the circular ADC distribution and calculate the circular spectrum. A digital phantom was used to simulate various diffusion patterns. Comparisons were made between the circular spectrum and regular DTI-based index maps. The results indicated that the zeroth- and second-order circular spectrum maps exhibited a strong consistency with the DTI-based mean diffusivity and linear indices, respectively, and the fourth-order circular spectrum map was able to identify the fiber crossings. MRI experiments were performed on seven healthy human brains using a 3T scanner. The in vivo fourth-order maps showed significantly higher densities in several brain regions, including the corpus callosum, cingulum bundle, superior longitudinal fasciculus, corticospinal tract, and middle cerebellar peduncle, which indicated the existence of fiber crossings in these regions.

Adult↗
PubMed1993

Diffusion and perfusion magnetic resonance imaging studies to evaluate a noncompetitive N-methyl-D-aspartate antagonist and reperfusion in experimental stroke in rats.

BACKGROUND AND PURPOSE: Diffusion magnetic resonance imaging (MRI) can quantitatively detect focal ischemic injury within minutes of onset, and perfusion MRI can evaluate the brain's microcirculation. N-Methyl-D-aspartate (NMDA) antagonists and reperfusion can reduce lesion size in stroke models. We used diffusion and perfusion MRI to evaluate the in vivo effects of a noncompetitive NMDA antagonist, CNS 1102, in a temporary ischemia model. METHODS: Sixteen Sprague-Dawley rats underwent suture occlusion of the middle cerebral artery. Fifteen minutes after occlusion, animals were randomly assigned to treatment with CNS 1102 (n = 10) or placebo (n = 6), receiving a bolus of 1.13 mg/kg at that time and an infusion of 0.785 mg.kg-1.h-1 for the next 165 minutes. The placebo group received a saline bolus and infusion. Diffusion MRI studies by a spin-echo technique were initiated 30 minutes after occlusion and repeated every 30 minutes for the next 3 hours. Perfusion MRI studies were obtained using echo-planar imaging after injection of superparamagnetic iron oxide particles, immediately before and 15 minutes after withdrawal of the occluder at 3 hours after middle cerebral artery occlusion. At 24 hours, the animals were clinically evaluated (scale of 0 to 5) and electively killed, and the brain was stained with triphenyltetrazolium chloride to evaluate infarct size. RESULTS: Diffusion imaging demonstrated markedly reduced ischemic lesion area in the CNS 1102 group during occlusion--10.5 +/- 7.3% (mean +/- SEM) of the ischemic hemisphere (optic chiasm slice) at 30 minutes after occlusion versus 50.0 +/- 2.7% of the hemisphere in controls (P < .02). With reperfusion after 3 hours of temporary ischemia, diffusion imaging documented an additional 29% reduction of the ischemic lesion area in the CNS 1102-treated group (P < .01) compared with the prereperfusion ischemic lesion area, with no change in the placebo group. During occlusion, perfusion imaging demonstrated a relative signal intensity decline of 31.5 +/- 7.7% in controls and 83.4 +/- 7.6% in the CNS 1102 group (P < .005), indicating better perfusion in the latter group. After removal of the occluder, perfusion improved in both groups and was not significantly different. Post mortem infarct volume was 53.8 +/- 20.0 mm3 in the CNS 1102 group and 216.8 +/- 16.1 mm3 in the controls (P < .0001). Clinical outcome at 24 hours was 1.1 +/- 0.4 in the CNS 1102 group and 4.0 +/- 0.5 (scale of 0 to 5) in the controls (P < .005). CONCLUSIONS: This study demonstrates that CNS 1102 reduces early postischemic injury as documented by diffusion MRI and improves perfusion as documented by perfusion MRI and that reperfusion confers additional reduction of ischemic lesion size.

Animals↗
PubMed2002

Diffusion- and perfusion-weighted MR imaging in a patient with acute demyelinating encephalomyelitis (ADEM).

To monitor changes of brain tissue metabolism in acute demyelinating encephalitis (ADEM), we examined a patient with suspected ADEM by serial MRI including diffusion- and perfusion-weighted imaging (DWI, PWI). Within the inflammatory tissue, the apparent diffusion coefficients were reduced, normal, and increased. Perfusion varied between reduced and normal values, except for small hyperperfused regions. Combining standard MRI with DWI and PWI may elucidate different overlapping phases in cerebral inflammation.

Adult↗
PubMed2004

Familial hemiplegic migraine: follow-up findings of diffusion-weighted magnetic resonance imaging (MRI), perfusion-MRI and [99mTc] HMPAO-SPECT in a patient with prolonged hemiplegic aura.

Familial hemiplegic migraine (FHM) is a rare inherited autosomal dominant disorder. Migraine aura may last up to several weeks and then resolve without sequel. We report a 21-year-old male with FHM since the age of 3 years. Diffusion-weighted magnetic resonance imaging (DWI), perfusion-MR imaging (P-MRI) and [99mTc] hexamethyl-propyleneamine-oxime-single photon emission tomography (HMPAO-SPECT) were performed on day 2, when he was somnolent with right-sided hemiplegia, on day 9 when a mild hemiparesis was still present and on day 24 after recovery. The right central region showed normal findings in DWI, whereas P-MRI and SPECT revealed hyperperfusion on day 2, less marked on day 9, and normal findings on day 24. In conclusion, this case report indicates for the first time, by means of SPECT, P-MRI and DWI studies, that even extremely long-lasting migraine aura is not associated with cerebral ischaemia. Therefore, it supports the revised International Headache Society criteria where the term 'persistent' aura is proposed.

Child, Preschool↗
PubMed1991

Diffusion of water in tissues and MRI.

The purpose of this paper is to present an overview of the diffusive behavior of water in biological tissues. The analysis shows that obstructive barriers would have to occupy very large volume fractions in order to account for the reduction in the diffusion coefficient (D) observed in biological systems. Generally, most models lead to the supposition that a substantial fraction (20-40%) of the cell water is hydration water, or that the diffusion coefficient of the cytoplasmic water is reduced substantially from the free water value. Thus, the conclusion that a substantial fraction of cell water has diffusive properties that are altered by the macromolecules of the cytoplasm seems inescapable. The impact of these findings on MRI remain to be determined.

Body Water↗
PubMed1994

Water diffusion and acute stroke.

The occlusion of the middle cerebral artery was used as an experimental acute stroke model in 30 cats. The diffusion of water was followed by diffusion-sensitized MRI between 1 and 15 h after induction of stroke. It is demonstrated that images representing the trace of the diffusion tensor provide a much more accurate delineation of affected area than images representing the diffusion in one direction only. The reason is that the strong contrast caused by the anisotropy and orientation of myelin fibers is completely removed in the trace of the diffusion tensor. The trace images show a small contrast between white and gray matter. The diffusion coefficient of white matter is decreased in acute stroke to approximately the same extent as gray matter. It is further shown that the average lifetime of water in extra and intracellular space is shorter than 20 ms both for healthy and ischemic tissue indicating that myelin fibers are permeable to water. The anisotropy contrast did not change before or after induction of stroke, nor after sacrifice. Together, these observations are consistent with the view that the changes in water diffusion during acute stroke are directly related to cytotoxic oedema, i.e., to the change in relative volume of intra- and extracellular spaces. Changes in membrane permeability do not appear to contribute significantly to the changes in diffusion.

Acute Disease↗
PubMed2006

Age-related water diffusion changes in human brain: a voxel-based approach.

The aim of the present study is to investigate age-related changes in water self-diffusion in cerebral white matter by analysing diffusion-weighted MRI from a sample of 54 healthy volunteers. A voxel-based analysis of the relative anisotropy and the apparent diffusion coefficients was performed by applying an optimized normalization protocol. Linear regression analysis revealed significant correlations with age in the corpus callosum, prefrontal regions, the internal capsule, the hippocampal complex, and the putamen. However, in other regions, such as those surrounding the ventricles, the insula, or the inferior frontal plane, significant correlations between age and ADC were observed, presumably as a result of morphological age-related variations. A mask procedure was carried out in order to distinguish between morphological involvement and real age-related white matter changes. Our results indicate that in interpreting the changes in each significant region it is necessary to proceed with precaution because the voxel-based statistical analysis might yield a mixture of two effects: (i) morphological changes that remain after the normalization procedure and (ii) actual diffusivity parameter changes. Anatomically defined regions of interest may help us to minimize morphologic involvement and draw comparisons with findings previously published.

Adult↗
PubMed2002

Magnetic resonance imaging of multiple sclerosis.

Although conventional magnetic resonance imaging (cMRI) is widely used for diagnosing multiple sclerosis (MS) and monitoring disease activity and evolution, the correlation between cMRI and clinical findings is far from strict. Among the reasons for this "clinical-MRI paradox," a major role has been attributed to the limited specificity of cMRI to the heterogeneous pathological substrates of MS and to its inability to quantify the extent of damage in the normal-appearing tissue. Modern quantitative MRI techniques have the potential to overcome some of the limitations of cMRI. Metrics derived from magnetization transfer and diffusion-weighted MRI enable one to quantify the extent of structural changes occurring within and outside macroscopic MS lesions with increased pathological specificity over cMRI. Magnetic resonance spectroscopy can add information on the biochemical nature of such changes, with the potential to improve significantly our ability to monitor inflammatory demyelination and axonal injury. Finally, functional MRI might provide new insights into the role of cortical adaptive changes in limiting the clinical consequences of white-matter structural damage. This review outlines the major contributions given by MRI-based techniques to the diagnostic work-up of MS patients, to the understanding of the pathobiology of the disease, and to the assessment of the effects of new experimental treatments.

Contrast Media↗
PubMed1996

Diabetes with the 3243 mitochondrial tRNALeu(UUR) mutation. Characteristic neuroimaging findings.

OBJECTIVE: To investigate the basis of central nervous system dysfunction in diabetes associated with the 3243 mitochondrial tRNA mutation, we studied neuroimaging findings in patients with this disease. RESEARCH DESIGN AND METHODS: We screened 205 diabetic patients. Those patients who had the 3243 mutation in leukocytes or muscle were enrolled. All the subjects underwent computed tomography (CT), magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), and N-isopropyl-p-[123I]iodoamphetamine ([123I]IMP) single-photon emission computed tomography (SPECT) of the brain. RESULTS: None of the nine subjects with the 3243 mutation had the typical clinical picture of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes, and none had neurological focal signs. CT or MRI revealed diffuse brain atrophy in three patients (33%) and cerebellar atrophy in one (11%). Abnormal high intensity areas were observed on MRI in five patients (56%). The overall prevalence of brain abnormalities was 56% (5 of 9) on CT and 78% (7 of 9) on MRI scans. MRA revealed no stenotic lesions. SPECT showed reduced accumulation of [123I]IMP in the right or left parieto-occipital region in eight patients (89%). CONCLUSIONS: Reduced accumulation of [123I]IMP in the parieto-occipital cortex was found in a high proportion of our subjects on SPECT. This imaging finding might be characteristic of diabetes associated with the 3243 mitochondrial tRNA mutation and may be a sign of latent central nervous system dysfunction.

Adult↗
PubMed2005

Prognostic significance of magnetic resonance imaging of bone marrow in previously untreated patients with multiple myeloma.

BACKGROUND: Magnetic resonance imaging (MRI) has been a useful technique for the assessment of patients with multiple myeloma (MM). We evaluated the prognostic significance of different MRI patterns in symptomatic patients with MM. PATIENTS AND METHODS: A total of 142 symptomatic MM patients underwent MRI before treatment. MRI patterns of involvement were correlated with known prognostic variables, including the International Staging System (ISS), response to treatment and survival. RESULTS: Focal marrow lesions were identified in 50% of patients, diffuse marrow replacement in 28%, a variegated pattern in 14% and normal pattern in 8%. When patients with the diffuse pattern were compared with patients with the other MRI patterns, they had features of more advanced disease such as higher ISS, anemia, hypercalcemia, elevated lactate dehydrogenase and extensive marrow plasmacytosis. Response rate was similar among patients with different MRI patterns. Median survival was 24 months for patients with the diffuse pattern, 51 months for those with the focal pattern, 52 months for those with the variegated pattern and 56 months for patients with the normal pattern (P = 0.001). The presence or absence of a diffuse MRI pattern separated patients with ISS stages I and II into two subgroups with significantly different survival times of 28 months and 61 months, respectively (P = 0.01). Furthermore, a diffuse MRI pattern predicted inferior outcome regardless of whether or not patients had received high-dose therapy with autologous stem cell transplantation. CONCLUSION: Diffuse marrow replacement on MRI adds to the evaluation of patients with multiple myeloma and their management.

Aged↗